Airbags and other pliable and inflatable restraints are being designed using releasable tethers to selectively modify the shape of the restraint, to provide the restraint with enhanced rigidity, and to control venting of the restraint during deployment. While it is necessary to securely retain the tether prior to activation of the inflatable device, at some point during or after deployment of the inflatable device it is frequently necessary to release the tether so that it no longer restrains the inflatable device. Thus, there is an ongoing need for tether retention systems of reduced cost and/or complexity which reliably retain the tether until release of the tether is desired, and which also reliably release the tether at the desired time.